Defensive Spray and Bear Spray are pretty much the same thing, the only difference is the label. In Canada, the label must say "Bear Spray" to be legal. The cans meant for humans are not.
Statistically, the spray works better than a gun. Some of that may be due to poor shot placement by gun owners, but a .44 mag does not always penetrate a bear's fat layer. Those bears are tough, but even they don't like the sensation on the pepper spray.